This invention relates generally to means for adjustably mounting a limit switch to a machine table or other supporting surface. More specifically, the invention relates to an adjustable mounting assembly which includes a movable switch supporting plate slidably mounted on a stationary base plate having an adjusting means interconnected between the two plates for precisely adjusting the position of the switch for accurate control of machinery.
Several different forms of adjustable mounting assemblies for precisely adjusting the position of a limit or stop switch carried thereby are known in the prior art. One such example is an automatic stop switch for a lathe as disclosed in U.S. Pat. No. 2,255,706 issued to L. H. Height on Sep. 9, 1941. In that example, a box containing a longitudinally displaceable, spring returned stop switch rod projecting therefrom is carried by an angle member extending downwardly from a block. The block is, in turn, slidably mounted on a rail having a guide rib extending therealong. A tie bolt connected through the block and angle member secures the block and box containing the stop switch rod at the desired position along the rail and guide rib relative to a moving part of a lathe. By simply loosening the tie bolt, the block, angle member and box containing the stop switch rod can be slid along the rail and rib to any desired position to selectively limit the length of movement of the moving lathe part.
An example of an adjustable mounting assembly for a pair of limit switches known in the prior art is that disclosed in U.S. Pat. No. 2,566,824 issued to G. K. Carlson on Sep. 4, 1951. That assembly incudes an operating nut which travels along a rotatable threaded shaft and a smooth guide shaft between a pair of switch contact arms. A frame of the assembly contains two blocks pivotally mounted thereon over two arc shaped slots in the frame. The contact arms are movably mounted on the sides of the blocks and extend upwardly on opposite sides of a contact finger carried by the nut such that they are positioned to engage the nut when the latter has traveled a predetermined distance. Each block contains a dog having a pin projecting therefrom into a different one of the slots in the frame. A pair of adjustment screws are interconnected between an edge of the frame and a different one of the dogs. Each of the screws contains a spring thereon which is maintained in compression between an edge of the frame and a dog. By turning one of the screws, one of the pins moves in the slot to cause the corresponding block to pivot so that its corresponding contact arm moves toward or away from one side of the contact finger of the traveling nut. The other block and its corresponding contact arm is adjusted in the same manner. Accordingly, the total length of travel of the nut can be precisely controlled within certain limits.
One difficulty encountered with the prior art adjustable mounting assemblies just described is the relatively large number of parts and complicated construction involved in each one. Another problem so far as the subject lathe stop switch is concerned is its limitation to use on machinery which has a rail and guide rib thereon properly aligned relative to the moving part which is to contact the switch.
By means of my invention, these and other difficulties encountered with prior art adjustable mounting assemblies for limit switches are substantially reduced if not altogether eliminated.